I've started playing with VOACAP to better plan and predict conditions on 27 MHz (CB). To my utter astonishment, VOACAP says that I won't be able to communicate on that frequency, regardless of antenna, desired reliability and length of path (tried very short with high take-off angle, medium and long ones).
VOACAP simply predicts that MUF will be around 14 MHz in the best of conditions (noon, artificially high SSN, long distance)!
I do understand that those predictions are statistical and don't mean "propagation conditions RIGHT NOW"; however, MUFDay of 0.00 means zero or very low probability of contact in the given month... and it is simply not true! Every day I get lots of transmissions from stations 500-1500 miles away, and I have a small whip antenna now!

Note that I'm sure I'm using VOACAP correctly because the results in a tutorial on voacap.com are very similar to mine (MUF of around 13 MHz, but they plan to transmit on 40 or 80 band so not an issue and their MUFDay is close to 1.00)

So how should I treat those predictions?..

  • Am I missing something obvious, either in using VOACAP or my understanding of propagation?
  • Is VOACAP useless for 10m band?
  • Maybe I should tweak some parameters?
  • $\begingroup$ Voacap is limited to ionospheric refraction. Higher frequency propagation is explained in this (and many other!) documents. itu.int/dms_pub/itu-r/opb/rep/R-REP-P.2011-1997-PDF-E.pdf $\endgroup$
    – F. Sessink
    Jun 25 at 15:48
  • $\begingroup$ Thanks @F.Sessink! Is there a propagation calculation software that would work at those frequencies? $\endgroup$
    – Alexander
    Jun 25 at 16:08
  • $\begingroup$ As far as I know there is no forecast or model. $\endgroup$
    – F. Sessink
    Jun 25 at 16:25

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